Qu’est ce qu’une image?

Laurent U Perrinet, INT

Cinésciences au collège Clair Soleil
23 Mars 2017
avec l'association Polly Maggoo

(AUTHOR) Hello, I am Laurent Perrinet from the Institute of Neurosciences of la Timone in Marseille, a joint unit from the CNRS and the AMU
(OBJECTIVE) in this short talk, I will be focus in highlighting some key challenges in modelizing visual perception and
(ACKNO) this endeavour involves different techniques and tools ... From the head on, I wish to thanks people who collaborated and in particular .. mostly funded by the ANR bala V1 (hansel wreeiswijk nowak) + ANR TRAJECTORY (o marrre bruno cessac palacios )
LONDON (Jim Bednar, Friston) great thanks to Stéphane for proposing me to present this work
(SHOW TITLE) I am interested in the link between the neural code and the structure of the world. in particular, for vision, I am researching the relation between the functional (in terms of the inferential processes leading to behaviour) organization (anatomy and activity) of low-level visual areas (V1) and the structures of natural scenes, that is of the images that hit the retina and which are relevant to visual perception in general.

so what is visual perception?

and at this instant, the sensed physical position is lagging behind (as represented here by $ au_s \cdot v 1~m$ ), that is, approximately at $45$ degrees of eccentricity (red dotted line),
while the position at the moment of emitting the motor command will be $.8~m$ ahead of its present physical position ($ au_m \cdot v$).
As a consequence, note that the player's gaze is directed to the ball at its present position (red line), in anticipatory fashion. Optimal control directs action (future motion of the eye) to the expected position (red dashed line) of the ball in the future --- and the racket (black dashed line) to the expected position of the ball when motor commands reach the periphery (muscles). This is obviously an interesting challenge for modelling an optimal control theory.

Khoei, Masson and LP (2017) PLoS CB http://invibe.net/LaurentPerrinet/Publications/KhoeiMassonPerrinet17

so let's go back on earth

... but first let now apply this model compensating for the aforementioned visual delays using a well described visual illusion: the flash-lag effect:

a first stimulus moves continuously across the screen along the central horizontal axis. In the FLE, as this moving stimulus reaches the center of the screen, a second stimulus is flashed just above it and in perfect vertical alignment. Despite the fact that the respective horizontal positions of each stimulus are physically identical when the flash occurs, the moving stimulus is most often perceived ahead of the flashed one.

debate for 80 years revived recently

motion extrapolation
differential latency
post-diction

we propose to extend the hypothesis previously proposed by Nihjawan that this effect is caused by the extrapolation of the stimulus' motion to compensate for the neural delay. However, this hypothesis was challenged by other hypothesis that this effect is due to either anatomy (differential latencies) or to the way visual awareness processes the sequence of events (the post-diction from Eagleman)

As a matter of fact, the motion extrapolation hypothesis was challenged because you can notice that the FLE is still present at initiation of the movement but this effect is not seen if the moving dot abruptly stops at the moment of the flash